Laboratoire de Glycochimie, des Antimicrobiens
et des Agroressources UMR 7378 CNRS

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Actualités et Publications

Curvature as a Collective Coordinate in Enhanced Sampling Membrane Simulations,

Bouvier, B.

J. Chem. Theory Comput. 2019.

The plasticity of membranes plays an important functional role in cells, cell components, and micelles, where bending, budding, and remodeling implement numerous recognition and communication processes. Comparatively, molecular simulation methods to induce, control, and quantitatively characterize such deformations remain scarce. This work defines a novel collective coordinate associated with membrane bending, which strives to combine realism (by preserving the notion of local atomic curvatures) and low computational cost (allowing its evaluation at every time step of a molecular dynamics simulation). Enhanced sampling simulations along this conformational coordinate provide convenient access to the underlying bending free energy landscape. To showcase its potential, the method is applied to three state-of-the-art problems: the determination of the bending free energy landscape of a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) bilayer, the formation of a POPE liposome, and the study of the influence of the Pseudomonas quinolone signal on the budding of Gram-negative bacterial outer membranes.

Conversion of Chitin in Ionic Liquids,

Hadad, C.; Husson, E.; Van Nhien, A. N.

Encyclopedia of Ionic Liquids 2019, 1-6.

Present in the exoskeleton of arthropods or in the cell walls of fungi, chitin belongs to the most abundant polysaccharides after cellulose and is composed of linear chains of β-(1 → 4)- N-acetyl-D-glucosamine. There are three types of chitins (α-, β-, γ-chitin) with different crystallographic structures. Among them, α-chitin, the most prominent form, is arranged in an antiparallel fashion and is found in both crustacean and insects’ sources [ 21]. Despite its excellent biodegradability, biocompatibility, antimicrobial activity, nontoxicity, low immunogenicity, and good mechanical properties, chitin remains underutilized. This limitation in terms of application is mainly due to: (i) the low extraction efficiency, (ii) the extraction costs excessively high and not environmentally friendly, and (iii) the lack of solubility of this hydrophobic biopolymer. To overcome this weak solubility, pretreatments (chemical, mechanical, enzymatic, …) are interesting alternatives by...

6th EPNOE International Polysaccharide Conference

José KOVENSKY, Véronique BONNET, Albert NGUYEN VAN NHIEN, Mariam NDOUR, Gaël HUET, Maria Emilia CANO

Aveiro PORTUGAL 21st– 25th October 2019

Le laboratoire LG2A a récemment participé à la 6ème Conférence Internationale sur les Polysaccharides, à Aveiro (Portugal) du 21 au 25 octobre. EPNOE a pour objectif de réunir des chercheurs du monde universitaire et du secteur industriel travaillant sur des thèmes de R & D liés aux polysaccharides ou intéressés par ce sujet, de diffuser les résultats et de promouvoir une plateforme de mise en réseau permettant des interactions étroites entre le monde universitaire et l'industrie.

Solvent- and catalyst-free transamidations of unprotected glycosyl carboxamides,

Bensalah, F. O.; Bil, A.; Wittine, K.; Bellahouel, S.; Lesur, D.; Markovic, D.; Laclef, S.

Org. Biomol. Chem. 2019.

The transamidation reactions of unprotected mono- and disaccharidic carboxamides with various primary and secondary arylic, heterocyclic or aliphatic amines are described. This new method is green and atom efficient and gives good to high yields. Notably, the conditions do not require either a solvent or a catalyst and give ammonia as a single by-product. The described coupling reaction is compatible with a variety of functional groups and was used in the synthesis of various glycosidic derivatives and biologically relevant glycolipids. A plausible reaction mechanism involving an intermolecular H-bond activation of the starting carboxamides is proposed.



Gwladys Pourceau, MCF au LG2A, a obtenu un financement ANR JCJC pour le projet CARBOPHOTON (2019-2022). Ce projet vise à développer et étudier de nouvelles procédures photocatalytiques de transformation sélective des sucres libres. Les collaborateurs impliqués sont Anne Wadouachi (Pr, LG2A, Amiens), Frédéric Sauvage (DR, LRCS, Amiens) et Hervé Vezin (DR, LASIR, Lille).

Ordering of Saturated and Unsaturated Lipid Membranes near Their Phase Transitions Induced by an Amphiphilic Cyclodextrin and Cholesterol,

Roux, M.; Bonnet, V.; Djedaïni-Pilard, F.

Langmuir 2019.

When inserted in membranes of dimyristoyl phosphatidylcholine (DMPC), methylated β-cyclodextrins with one (TrimβMLC) or two (TrimβDLC) lauryl acyl chains grafted onto the hydrophilic cavity exert a “cholesterol-like ordering effect”, by straightening the acyl chains in the fluid phase at temperatures near the chain melting transition. This effect may be related to pretransitional events such as the “anomalous swelling” known to occur with saturated phosphatidylcholine membranes. To investigate this model, order profiles and bilayer thicknesses of DMPC and unsaturated 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) membranes containing amphiphilic cyclodextrins or cholesterol were determined by deuterium NMR. The pure lipid membranes display both a qualitatively similar chain ordering upon cooling in the fluid phase, more important at the chain extremity, which gets more pronounced near their fluid-to-gel transitions. Both membranes show a bilayer thickness increase by ∼0.5 Å just above their transition, as observed previously with saturated phosphatidylcholines of various chain lengths. Membrane-insertion of 5% TrimβMLC or cholesterol induces an important ordering of the DMPC acyl chains just above the transition, which is also more pronounced at the chain extremity. There is an additional increase of the bilayer thickness, most probably due to a deep insertion of these amphiphilic molecules, facilitated by increased bilayer softness in the anomalous swelling regime. These effects are more important with TrimβMLC than with cholesterol. By contrast, no enhanced acyl chain ordering was observed when approaching the transition of TrimβMLC-containing POPC membranes, as a possible consequence of an eventual lack of anomalous swelling in unsaturated lipid membranes. Insertion of higher concentrations of TrimβMLC was found to induce a magnetic orientation of the DMPC membranes in the fluid phase with 10% of this derivative, coupled with the appearance of a broad isotropic component when the concentration is raised to 20%. No membrane orientation or isotropic component was detected with TrimβMLC-containing POPC membranes.

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